The invention relates to a spinning assembly for a wrapped yarn spinning machine with a hollow spindle, said spindle carrying a co-rotating binding thread wrapping, covering material and being disposed between a delivery device for a staple sliver to be covered and a removal apparatus for the wrapped yarn. The spindle is further surrounded in the vicinity of the binding thread with a stationary balloon limiter, with which limiter a likewise stationary screen for the binding thread is associated, said screen being located between the delivery device and the balloon limiter, said screen comprising a passage for the staple sliver.
A spinning assembly of this type is known from German Offenlegungsschrift No. 29 28 890. The balloon limiter surrounding the hollow spindle is covered by a lid, in which only one feed opening is provided for the sliver, and therefore completely encapsulates the hollow spindle and binding thread from the ambient atmosphere. This is intended to ensure that the binding thread does not pick up any fiber fly or the like, floating in the air, as the balloon is formed, while it is being wrapped around the sliver. Such inclusions of fiber fly not only have a detrimental effect upon the appearance of the finished-wrapped yarn, but can occasionally even lead to accumulations of material and hence to thread breaks. In the known device, the lower end of the hollow spindle is connected to a pneumatic source, which generates an air stream in the direction of the covered or wrapped yarn, in such a way that the accumulation of fiber fly or the like within the hollow spindle is to be avoided.
It has been found that the desired goals or objects can be achieved only very imperfectly with the known device. In particular, the pneumatic source connected to the hollow spindle continually draws air through the feed opening of the balloon limiter lid. This air which is drawn in, necessarily brings fiber fly with it, which, once inside the balloon limiter, is bound to penetrate the interior of the hollow spindle and therefore is often incorporated into the resultant wrapped yarn. Fiber fly which enters through the feed opening of the balloon limiter lid is practically impossible to eliminate from the vicinity of the resultant yarn.
In a device according to German Offenlegungsschrift No. 29 13 762, therefore, in order to avoid the disadvantages outlined above, the binding thread is subjected to an air stream prior to its entry into the hollow spindle, and a mechanical means of stripping fiber fly off the filament thread is also provided. For this purpose, the lid of the balloon limiter is not mounted in a stationary fashion on the balloon limiter itself, but rather the lid is designed as a rotating disk, mounted on the spindle head. This disk leaves an annular slit free between itself and the wall of the balloon limiter, through which special structural designs permit air to flow from above into the interior of the balloon limiter, whereupon the air is guided out of the balloon limiter again further down. The disk is made convex on its upper surface in such a way that the binding thread, brought out through the abovementioned annular slit from the balloon limiter, can abut this convex surface of the rotating disk, thereby preventing accumulations of fiber tufts.
In this device, the increased energy consumption is disadvantageous, because the co-rotating disk results in an increase in inertia. In addition, the cost of manufacturing such a device is relatively high.
An object of the present invention is to avoid the disadvantages of the abovementioned devices and to provide a wrapped yarn spinning machine wherein fiber-fly accumulations in the binding thread can be avoided without increasing the energy demand. This goal is achieved in preferred embodiments of the present invention by providing a screen constructed as a screen plate and located at an axial distance from the balloon limiter.
The features of the invention ensure that an air stream is generated within the balloon limiter without using suction devices of any kind, the stream flowing upward from below and being deflected radially outward through the gap between the upper end of the uncovered balloon limiter and the screen plate, and escaping thereat. Thus, a situation is created in which the air stream is directed opposite to the movement of the sliver travelling into the hollow spindle as well as the binding thread travelling into the hollow spindle, so that there is no way in which fiber fly can penetrate the interior of the hollow spindle. The rotating hollow spindle generates the abovementioned air stream itself in the device according to preferred embodiments of the invention.
Further advantageous embodiments and features of the invention are set forth in the claims and the description. Thus, it is advantageous for the screen plate to comprise a threading slit. When beginning spinning with the spinning assembly, for example, after a thread break, it is conventional to feed an auxiliary thread through the hollow spindle in a direction opposite to the subsequent production direction. This auxiliary thread must be connected with the binding thread and the sliver, and must therefore be guided through the passage located in the screen for the staple sliver. To facilitate the operating task, a radial slit is provided, extending outward from the passage, through which slit the auxiliary thread can simply be inserted from outside in through the passage. The threading slit has dimensions such that the sliver, guided through the passage in the screen plate, cannot inadvertently enter this slit during normal spinning.
With the structural dimensions for the balloon limiter and hollow spindle which were used on the application date, it is advantageous for the interval between the balloon limiter and the screen to be approximately 15 to 25 mm. With these dimensions, optimum flow conditions result.
In another embodiment of the invention, a preferably adjustable suction device is associated with the screen plate. The suction device is advantageously located on the side away from the balloon limiter. This means that the air stream emerging from the balloon limiter, deflected radially outward by the screen, will not be adversely affected by the suction. In addition, this is intended to draw off the fly which enters on the sliver itself through the passage in the screen. In order to prevent product fibers from being unnecessarily drawn off, this suction is preferably made adjustable in such a way that it can assume different positions relative to the sliver during operation and during the start of spinning. Provision is made for the air stream not to have a directly disadvantageous effect on the sliver during operation, so that product fibers will not be drawn off unnecessarily, but only the upper edge of the screen plate, essentially, will be kept clean. During the start of spinning, therefore, the suction can be brought closer to the passage in the screen so that the sliver can be held in the correct position for starting spinning when spinning begins.
It is advantageous in certain preferred embodiments for a tube surrounding the sliver to be associated with the screen plate, the tube extending from the screen plate to the delivery device and/or the hollow spindle. In this way, the path of the sliver before it enters the hollow spindle is largely enclosed whereby a slit required for threading can be provided if desired. This enclosure ensures that individual fibers cannot separate from the sliver.
As far as the invention's design is concerned, it is advantageous in especially the preferred embodiments for a common screen plate to be associated with a plurality of balloon limiters. The screen plate is therefore designed, so to speak, as a lattice extending over a plurality of spinning units, resulting in considerable simplification of manufacture.
These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings which show, for the purposes of illustration only, several embodiments in accordance with the present invention, and wherein: